https://online2.tingclass.net/lesson/shi0529/0001/1240/21-14.mp3
https://image.tingclass.net/statics/js/2012
30. There is no easy solution to Japan’s labor________.
A. decline B. vacancy C. rarity D. shortage
<decline>
decline 下降，下垂
</decline>
<vacancy>
vacancy 空位（無(wú)人占用）空置，空缺
</vacancy>
<rare>
rare 稀少的，珍貴的
rarity 稀少
rare book 珍藏本
rare animal 珍奇動(dòng)物
best seller 暢銷(xiāo)書(shū)
</rare>
empty 空的
vacant 空洞的，言之無(wú)物
bald 禿的
bare 部分赤裸
nud 全身赤裸
